Problem when syncing contacts to iphone

Hi there,

I set up a new oc instance and now I have problems syncing the contacts from oc 10.0.4 with iPhone 8 (iOS 11.2.6).

the phone does not sync all the contacts. I created 2 addressbooks. At oc all contacts are available. At the iPhone:

addressbook 1: 349 of 431
addressbook 2: 37 of 40

Any idea?

Thanks for your help.